There are machine-to-machine (M2M) information collecting systems that transfer data between a machine and a machine that are able to communicate with each other. In some existing M2M information collecting systems, M2M service providers use dedicated wire lines for individual machines. However, laying dedicated wire lines leads to very high cost. Some M2M information collecting systems use mobile networks of cellular phones that have spread throughout the world. However, the communication speed of mobile networks is low, and moreover their communication cost is high.
Accordingly, there has been also proposed a scheme in which transfer of data between a machine and a machine is realized by wireless ad hoc communication, and data is aggregated at a gateway connected to a mobile network or a dedicated line. FIG. 22 is an explanatory diagram illustrating an example of an M2M information collecting system. An M2M information collecting system 200 illustrated as FIG. 22 includes a machine 201, a communication interface (hereinafter, simply referred to as IF) 202, an access network 203 such as a wireless ad hoc network, a gateway 204, a core network 205, and a server 206. The machine 201 uses the communication IF 202 to establish a connection with the server 206 via the access network 203, the gateway 204, and the core network 205. Then, after establishing a connection with the server 206, the machine 201 transmits data from the machine 201 to the server 206.
However, to build a wireless ad hoc network, the placement density of machines 201 has to be increased, leading to very high cost.
Accordingly, M2M information collecting systems exist which use a Delay Tolerant Networking (DTN)-based store-carry-forward communication scheme in areas where there is no communication infrastructure, without increasing the placement density of machines 201. FIG. 23 is an explanatory diagram illustrating an example of an M2M information collecting system. An M2M information collecting system 300 illustrated as FIG. 23 includes a machine 301, a communication IF 302, a first short-range wireless network 303, a relay device 304, a second short-range wireless network 305, a fixed access point (hereinafter, simply referred to as AP) 306, and an access network 307. Further, the M2M information collecting system 300 includes a gateway 308, a core network 309, and a server 310. In the M2M information collecting system 300, the relay device 304 based on the store-carry-forward communication scheme physically moves while being carried by a human being, a vehicle, or the like, in the area between the first short-range wireless network 303 and the second short-range wireless network 305 where no communication infrastructure exists.
The relay device 304 moves into the area of the first short-range wireless network 303, communicates with the machine IF 302 of the machine 301 located within the first short-range wireless network 303, and receives information from the machine 301. Further, the relay device 304 passes through the area between the first short-range wireless network 303 and the second short-range wireless network 305 where no communication infrastructure exists, and moves into the area of the second short-range wireless network 305. The relay device 304 moves into the area of the second short-range wireless network 305 and communicates with the second short-range wireless network 305. Further, the fixed AP 306 receives data on the machine 301 via the second short-range wireless network 305 from the relay device 304 that has moved into the area of the second short-range wireless network 305, and transmits the received data to the gateway 308 via the access network 307. Further, the gateway 308 transmits the data received via the access network 307 to the server 310 via the core network 309.
As a result, in the M2M information collecting system 300 illustrated as FIG. 23, the relay device 304 based on the DTN scheme complements the communication in the area between the first short-range wireless network 303 and the second short-range wireless network 305 where no communication infrastructure exists. Then, in the M2M information collecting system 300, data from the machine 301 is transferred to the server 310.
The followings are related arts:                Japanese Laid-open Patent Publication No. 2002-290563;        Japanese Laid-open Patent Publication No. 2006-80782;        K. Fall, “A Delay-Tolerant Network Architecture for Challenged Internets”, in Proc. ACM SIGCOMM, pp. 27-34, 2003;        Z. Zhang, “Routing in intermittently connected mobile ad hoc networks and delay tolerant networks: overview and challenges”, IEEE Communications Surveys Tutorials 8(1), pp. 24-37, 2006;        Vahdat, D. Becker, “Epidemic routing for partially connected ad hoc networks”, Technical Report CS-2000-06, 2000;        R. Groenevelt, P. Nain and G. Koole, “The Message Delay in Mobile Ad Hoc Networks.,”Performance Evaluation, vol. 62, pp. 210-228, October 2005;        T. Matsuda, T. Takine, (p,q)-“Epidemic Routing for Sparsely Populated Mobile Ad Hock Networks., Selected Areas in Communications”, IEEE Journal, vol. 28. pp. 783-793, 2008;        Lindgre, A. Doria and O. Schelen, “Probalistic Routing in Intermittently Connected Networks.”, in Proc. SAPIR Workshop, pp. 239-254, August 2003;        Balasubramanian, B. Levine and A. Venkataramani, “DTN routing as Resource Allocation Problem.”, in Proc. ACM SIGCOMM, pp. 373-384, August 2007;        M. Garetto, P. Giaccone, E. Leonardi, “Capacity scaling in delay tolerant networks with heterogeneous mobile nodes”, in Proc. ACM Mob/Hoc, pp. 41-50, 2007;        W. Zhao, Y. Chen, M. Ammar, M. Corner, B. Levine, and E. Zegura, “Capacity Enhancement using throwboxes in mobile tolerant network”, SCS Technical report GIT-CSS-06-04, 2006;        Hull, V. Bychkovskiy, K. Chen, M. Goraczko, E. Shih, Y. Zhang, H. Balakrishnan, S. Madden, CarTel: “a distributed mobile sensor computing system”, in: Proc. SenSys, vol. 2, pp. 1407-1418, 2006;        W. Zhao, M. Ammar, E. Zegura, “Controlling the mobility of multiple data transport ferries in a delay-tolerant network”, in: Proc. IEEE INFOCOM, vol. 2, pp. 1407-1418, 2005; and        S. Yamamura, A. Nagata, M. Tsuru, H. Tamura, Virtual segment: “store-carry-forward relay-based support for widearea non-real-time data exchange”, Simulation Modeling Practice and Theory SIMPAT, vol. 19, no. 1, pp. 30-46, January 2011.        